A button and a text with icon around it.

FullIconButton 继承自MaterialButton，在构造函数里我加了这些属性

    double minWidth,
    double height,
    Widget leftIcon,
    Widget topIcon,
    Widget rightIcon,
    Widget bottomIcon,
    EdgeInsetsGeometry textPadding,

我们可以定义宽高，上下左右图标，还有文字和图标的间距，这样用起来会比较方便了。当然如果你有其他需求一样可以自己加进去。 另外我们用了Column,Row,Offstage；Column控制竖排的widget，Row控制横排的widget，Offstage控制icon的显示或隐藏，Offstage 有2个属性offstage和child，其中offstage=true时Offstage 就不显示了。 下面我们用下这个FullIconButton

FullIconButton(
  label: Text("GitHub登录"),
  color: Colors.blue,
  textColor: Colors.white,
  onPressed: () {},
  minWidth: double.infinity,
  leftIcon: Image.asset(
    "images/icon_github.png",
    width: 24,
    height: 24,
    color: Colors.white,
  ),
  rightIcon: Icon(Icons.group),
  topIcon: Text("我是👆"),
  bottomIcon: Text("我是👇"),
  textPadding: EdgeInsets.only(left: 10, right: 10),
)

效果如下：

当然四周定义的是widget，所以你可以放任何widget进去，不只是icon。通过这个自定义Button，我们可以定义任何我们想要的通用的widget，不明白或者遇到问题的时候查看下源码是怎么做的就可以了。

添加了FullIconText

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